1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, which are used in an image forming apparatus, such as a printer or a digital copying machine, wherein an image signal produced by reading an image of an original by image input means such as a scanner is subjected to image processing such as tone processing, and the processed image is printed out onto paper by binary image output means of, e.g., an electrophotographic type.
2. Description of the Related Art
In a conventional tone process wherein output pixel values (binary) are determined by comparison with threshold values that change cyclically as in a regular pattern dither method, only a screen pattern, which is output as an image and varies in a simple fashion relative to an input image signal, is produced. It is not possible, therefore, to form a screen pattern that varies in a complex fashion in accordance with a gray level of the input image signal. In addition, an enormous memory capacity is required to store binary screen patterns corresponding to all input image signals.